455 



According to the table the amplitude e, diminishes markedly as we pass from February to March, or 

 from October to September. This wo should of course expect, but it does appear a little curious that c\ 

 shows no marked further tendency to reduction as we approach midwinter. 



In the 12-hour wave the phase angle varies somewhat irregularly from month to month, but the 

 irregularity is no greater from April to August than during the rest of the year. The times of occurrence 

 of the positive crest (in either forenoon or afternoon) are approximately as follows : 



Year 3h. 50m., midsummer 4h. Om., equinox Ih. Om., midwinter 4h. 30m. 



The amplitude r* seems greatest in winter and least in summer. 



The tendency in f->/f\ to increase as we pass from summer to winter is even more marked than in 

 temperate climates. 



3. In examining the data one could not but be impressed by the variability of the temperature, 

 especially in winter. In the middle of an intensely cold period there would appear a sort of oasis of 

 warmth. Table III. has been prepared with a view to bringing out this fact. It gives the mean tempera- 

 ture of the hottest and coldest days of each month, as derived from the 2-hourly readings. The days 



TABT.E III. Hottest and Coldest Days. 



were all taken from midnight to midnight. If one had interpreted a "day " as any 24 consecutive hours, 

 the difference between the hottest and coldest " days " would, of course, have been in general slightly 

 greater. The table gives results for each individual month from February, 1902, to January, 1904, and 

 also the means from the two years. In November and December, 1903, and January, 1904, the number 

 of observation hours was reduced during the night. Allowance was made for this in calculating the mean 

 temperature, use being made of the diurnal changes of temperature observed in the corresponding 

 midsummer months of 1902 and 1903. 



April, 190.), was the only month in which no day had a mean temperature exceeding 0' F. 



The difference between the hottest and coldest days of the month is much less in summer than in 

 winter. There is not nearly so much difference between the temperatures of the hottest days of the 

 different months as between the temperatures of the coldest days. In both years the absolutely coldest 

 day occurred in August, and the hottest in December. The latter was the only mouth of the year in 

 which the hottest day had a mean temperature in excess of the freezing-point. 



s? 4. The minimum thermometer was read and reset every two hours. Each value recorded thus 

 represents the lowest temperature during the previous two hours. Comparing each minimum reading 

 with the mean of the two ordinary thermometer readings at the beginning and end of the 2-hour 

 interval, one gets an idea of the variability chiefly the a periodic variability of temperature throughout 

 the day and throughout the year. 



